By Mark Knauer, North Carolina State University
Last week I had the opportunity to attend a series of nutrition seminars and present on sow body condition management. One of the attendees posed the question “why do we still have sow herds that are fat?” At a break in the program I tracked down the attendee to ensure my answer was sufficient and to see what perspectives I may gain. The attendee believed that farmers did not understand the true cost of having fat sows. Later on that same day a large producer was looking to develop a model to understand what fat sows cost. Hence with the available data I have, I will put together an example cost estimate for having a fat sow herd.

A fat sow herd hits your pocketbook twice. Not only does it take excess feed (resulting in greater feed costs) to create a fat sow, heavy sows wean fewer piglets. In some of our original work on sow condition management, we looked at two farms (Farm A & B) within the same production system. Same genetics, feed from the same feed mill, same facilities. The main difference between the two farms was the people adjusting the feed drop boxes. Average sow weight at Farm A and B was 546 and 486 pounds, respectively. A difference of 60 pounds. Assuming a feed:gain ratio of 4.5 (Knauer et al., 2008), 270 pounds of extra feed would be needed per sow. Assuming an average parity of 3.5, 193 pounds of feed per sow per year. If feed cost is $.10 per pound. x 193 pounds of feed = $19.30 in extra feed costs per sow per year.

Besides greater feed costs, over conditioned sows wean fewer pigs. In studies where we have captured sow weight, a 100 pound increase in sow weight was associated with .55 fewer piglets weaned. Hence farm A, being 60 pounds heavier, would wean .33 fewer piglets per litter x 2.5 litters per year x $35 per weaned pig = $28.88 in lost piglet throughput. Adding together the extra feed costs and reduced piglet throughput associated with overconditioned sows, we can see Farm A was costing the producer nearly $50 per sow per year ($19.30 + $28.88 = $48.18).

While these calculations are a good start, arguably more work is needed to better understand the true cost of maintaining a fat sow herd. Besides increased feed costs and reduced reproductive performance, fat sow herds may have poorer longevity as sows are removed for being too big. It is assumed lighter sows will eat more in lactation, yet this increased feed cost should be more than offset by enhanced subsequent farrowing rate and litter size. In summary, fat sows are costly. Perhaps better understanding the true cost of having a fat sow herd will encourage producers to better manage sow body condition.

References
Knauer, M. T., M. T. See, J. A. Hansen, A. L. P. de Souza, and D. C. Kendall. 2008 (Abstr.). Response of cull sows to ad libitum feeding. J. Anim. Sci. 86(E-Suppl. 3):64.